The document discusses the history and types of vapor absorption machines (VAM) invented in the late 19th century, highlighting both steam and direct-fired models. It explains the principles of refrigeration, the operation of VAM, and the technical components involved in the absorption process, including the roles of refrigerants and heat sources. Additionally, it addresses efficiency measures, factors affecting crystallization, and the use of inhibitors in maintenance.

1. 1
VAPOUR ABSORPTION
MACHINES
BRIEF HISTORY
•-INVENTED BY FRENCH SCIENTIST IN 1890 BY
FERDINAND CARRE
• -1ST
MACHINE WAS SINGLE EFFECT MACHINE
•-JAPAN INTRODUCED 1ST
DOUBLE EFECT
MACHINE
•-INDIA 1ST
MACHINE WAS INSTALLED IN 1970
•-INDIGENEOUSLY MADE 1ST
MACHINE IN INDIA IN
1989 BY THERMAX ENGGINEERING

2. 2
TYPES OF VAM
• 1. STEAM FIRED VAM
• A. SINGLE EFFECT
• B. DOUBLE EFFECT
• 2. DIRECT FIRED VAM
• A. HSD FIRED
• B. LDO FIRED
• C. NG FIRED
• 3. HOT WATER FIRED VAM

3. 3
BASIC TERMS IN
REFRIGERATION
• DEFINITION OF REFRIGERATION
• -REFRIGERATION IS THE PROCESS OF COOLING
BY REMOVAL OF HEAT.
• MECHANICAL REFRIGERATION
• -THIS TYPE OF SYSTEMS WE USE IN COMMON e.g.
DOMESTIC REFRIGERATOR AND ROOM A.C.
• THIS TYPE OF REFRIGERATION CONSISTS OF
FOLLOWINGS:
• 1.EVAPORATOR
• 2.COMPRESSOR
• 3.CONDENSER
• 4.EXPANSION DEVICE

4. 4
VAM Vs.MECHANICAL
REFRIGERATION
• DIFFERENCE FROM MECHANICAL
REFRIGRATION
• ANY VAM DIFFER FROM MECHANICAL
ONE AS IT DOES NOT HAVE ANY
COMPRESSOR AND EXPANSION
DEVICE.

5. 5
SOME MORE DEFINITIONS
• HEAT: HEAT IS THE FORM OF ENERGY.
• HEAT FLOWS DOWNHILL
• SENSIBLE HEAT:HEAT WHICH CAN BE SENSED AND
MAESURED IN FACT THIS IS MOVEMENT OF
MOLECULES WITHIN THE SUBSTANCE & NO
CHANGE OF STATE OCCURS DURING SENSIBLE
HEATING.
• LATENT HEAT:IT IS THE ENERGY OF MOLECULES
SEPARATION ,THIS CANNOT BE MEASURED ON A
THERMOMETER AND CHANGE OF STATE OCCURS .
• ENTHALPY:
• IT IS THE AMOUNT OF TOTAL HEAT i.e. SUM OF
SENSIBLE AND LATENT HEAT.

6. 6
SOME MORE DEFINITIONS
TONNE OF REFRIGERATION= ONE
TONNE ICE AT 320
F WHEN MELTED IN
24 Hrs.
WE WILL BE INSTALLING TWO VAM HOT
FIRED EACH HAVING CAPACITY
210TR.
DRIVING HEAT MEDIA:HOT WATER 74M3

7. 7
HOW DOES THE VAM WORKS
• -BOILING POINT OF WATER IS A FUNCTION
OF PRESSURE.
• -AT ATMOSPHERIC PRESSURE WATER
BOILS AT1000
C,WHEN MAINTAINED AT HIGH
VACUUM, WATER WILL BOIL AT 6MMHg(abs.)
at 3.7o
c only.
• -LiBr HAS TENDENCY TO ABSORB WATER
DUE TO ITS CHEMICAL AFFINITY.AT HIGHER
CONCENTRATION AND LOWER
TEMPERATURE LiBr ABSORBS WATER
VAPOUR(REFRIGENT) VERY EFFECTIVELY.

8. 8
Contd.
• -AS LiBr BECOMES DILUTE IT LOSSES ITS
CAPACITY TO ABSORB WATER VAPOUR. IT
THUS NEEDS TO BE RECONCENTRATED
USING AHEAT SOURCE. HEAT SOURCE MAY
BE STEAM OR HOT WATER.
• -THE HEATING CAUSES THE SOLUTION TO
RELEASE THE ABSORBED REFRIGERANT IN
THE FORM OF VAPOURS. THIS VAPOUR IS
COOLED IN A CHAMBER TO BECOME LIQUID
REFRIGERANT.

9. 9
The Principle of Absorption
Cooling
• The two basic principles on which all air conditioning and
refrigeration plants operate are :
1) When a liquid evaporates, it absorbs heat, and when it
condenses it gives up that heat. This heat is called the
latent heat of evaporation, and latent heat of
condensation respectively.
2) Boiling point of liquid at Pressure.
* i.e Boiling point increases as pressure increases Boiling
point decreases if pressure decreases
* For example, at atmospheric pressure (760 mm of Hg
absolute) water boils at 100 0
C & at 6mm Hg absolute
pressure it boils at 3.7 0
C

10. 10
• The absorption cooling works on the affinity of
some pairs of chemical to dissolve in one
another. For example, Lithium bromide solution
has affinity towards water, water has affinity
towards Ammonia etc.
• This affinity depends on two factors .
Temperature & the concentration of the solution.
(1)Affinity is directly propotional to Concentration
(2)Affinity is inversly proportional to temperature

11. 11
Parts of VAM
1) Evaporator
2) Absorber
3) Regenerator
4) Condenser
Other parts are absorbent pump, refrigerant
pump, purge unit, LTHE, HTHE, HR,
DHE.

12. 12
In the Vapour Absorption Chillers, a low
pressure (vacuum) is maintained in the
Evaporator. At this pressure the refrigerant
boils at very low temperature. This boiling
causes the refrigerant to absorb heat from
the medium being cooled, thus, lowering the
temperature.

13. 13
• On absorbing the heat the refrigerant gets
vapourised. The refrigerant vapours thus
formed tend to increase the pressure in
the vessel. This will in turn increase the
boiling temperature and the desired
cooling effect will not be obtained. So, it is
necessary to remove the refrigerant
vapours from the vessel.

14. 14

15. 15
• A liquid having affinity towards the refrigerant
vapour is sprayed in the absorber which absorbs
the vapour and maintains the low pressure in the
shell.
• As the absorbent absorbs the refrigerant vapour,
it becomes dilute & losses its capacity to further
absorb refrigerant vapours.
• To maintain continuous cycle, it is essential that
the absorbent is enriched to its original level of
concentration and the refrigerant vapours are
condensed back to the liquid.

16. 16
SINGLE EFFECT VAM

17. 17
• This is achieved by pumping the dilute solution
continuously from absorber to the generator. In
the generator the addition of heat boils off the
refrigerant from the absorbent and the absorbent
regains its original level of concentration. The re-
concentrated absorbent returns to the absorber
to resume the absorption process.
• The refrigerant vapour .released. in the
generator flows to the condenser.
• In the condenser cooling water is circulated
through the coils, which picks up the heat carried
by the refrigerant vapour and vapour condenses
back to the liquid phase. The condensed liquid is
returned back to the evaporator thus completing
the absorption cycle.

18. 18

19. 19
Coefficient Of Performance
• Coefficient of performance (COP) is the
measure of efficiency in a heat pump or
refrigerating machine.
• COP = Refrigeration effect/Heat input
• COP for different types of heat pumps are
as follows : -
Double effect type = 1.15
Single effect type = 0.6-0.7

20. 20
Factors affecting
CRYSTALLISATION
Low solution temperature
• Cooling water temp. low
• Dilute solution temp. low
• LTHE spray solution temp. low
2)High concentration
3)Excess heat input
• High steam pressure
• Steam control valve passing
• Contamination of LiBr in evaporators

21. 21
Corrosion inhibitor
Lithium Molybdate (Li2MoO4)
While startup: 400 ppm
During normal operation: 100 to 150 ppm
• If inhibitor is more than 150 ppm, it makes
LiBr precipitates
Additive
Additive
Octyl Alcohol (2-Ethyl 1-Hexanol)
Octyl Alcohol (2-Ethyl 1-Hexanol)
It is added to increase effect of absorbent.
It is added to increase effect of absorbent.
Excess additive could form sludge in heat exchangers
Excess additive could form sludge in heat exchangers